What about Giles? I know he has a terrible past, but he's clearly fully on the side of good by the time we meet him, and he never puts a foot wrong, does he?
Murdered Ben because he felt Buffy wouldn't be able to and then there's "Helpless".
Or Xander - ok, kind of a wuss, but he is surrounded by people with superpowers and he still does his best - barring a couple of unfortunate incidents.
He's portrayed as a useless appendage that nobody truly appreciates. I will give them the fact that he was the one who stopped Dark Willow, at least.
Then there's the fact that he walked out on his wedding for no apparent reason other than Joss' bizarre obsession with father-bashing. The only good father I can think of in anything Joss has written was Fred's.